1. Field of the Invention
The present invention relates to a bonding apparatus, particularly to a bonding apparatus by which a stratified film consisting of a photosensitive resin layer and a light-transmissible resin film is bonded, under pressure, to a base plate or a panel for a printed circuit board.
2. Description of the Background
In a conventional bonding apparatus, stratified films are sequentially bonded to base plates for printed circuit boards, respectively, as the base plates are sequentially conveyed on a roller conveyor or the like and a continuous stratified film is cut off to make each bonded film have a length corresponding to that of the base plate. Before the continuous stratified film is cut off, it is bonded to the base plate while a tension is applied to the film. Since the unbonded portion of the cut-off film is free to sag due to the effect of gravity on that portion, an air bubble may be produced between the bonded film and the base plate; alternatively the film may be wrinkled. In order to prevent such phenomena, film trailing edge holding members, each of which is a vacuum suction bar having a film sucking function, are provided at the peripheral portions of upper and lower heat and pressure bonding rollers so as to hold the trailing edge portions of the cut-off films and apply a tension to those portions. The film trailing edge holding .members are moved by pneumatic cylinders, completely independently of means for rotating the heat and pressure bonding rollers. An art relating to the film trailing edge holding members is described in the Japanese Patent Application (OPI) No. 205140/86 (the term "OPI" as used herein means an "unexamined published application").
In the conventional art mentioned above, the rotative circumferential velocity of the heat and pressure bonding roller, which is equal to the speed of the bonding of the stratified film to the base plate, needs to be changed if the efficiency of the bonding is to be enhanced by increasing the velocity. When the rotative circumferential velocity of the roller is changed, the speed of the movement of the film trailing edge holding member needs to be changed depending on the circumferential velocity of the roller after the velocity is determined. This is a first problem. If the bonding apparatus is so large in size as to be capable of bonding a film of large width to a base plate, the film trailing edge holding member and the pneumatic cylinders need to be so large in size and weight that it is difficult to smoothly move them. This is a second problem. If the width of the stratified film to be bonded to the base plate is small, the sucking force of the film trailing edge holding member on the film is reduced so that the member cannot hold the film, thus making it likely that an air bubble is made between the bonded film and the base plate or and the film is wrinkled. This is a third problem.
The present invention was made in order to solve these three and other problems. Accordingly, it is an object of the present invention to reduce the likelihood that an air bubble is made between a film and a base plate or that the film is wrinkled.
It is another object of the present invention to automatically change the speed of the movement of a film trailing edge holding member depending on the rotative circumferential velocity of a heat and pressure bonding roller.
It is yet another object of the present invention to hold the rear edge of a film, regardless of the width of the film, when the film is bonded to a base plate or a panel.
The above-mentioned and other objects and novel features of the present invention will be apparent from the description herein and the drawings attached hereto.
The above-mentioned problems are solved by providing a bonding apparatus in which a pressure bonding roller is provided so that a film having a length corresponding to that of a base plate or a panel is bonded to the film bonding surface of the base plate by the roller; a film trailing edge holding member is rotatably supported near the peripheral surface of the roller; and the holding member holding the trailing edge portion of the film cut off to the desired length is moved to a position near the mutual contact surfaces of the roller and the film on the base plate or the panel, at a speed equal to or slightly less than the rotative circumferential velocity of the roller. The bonding apparatus is characterized by a film trailing edge holding member movement speed control means for automatically changing the speed of the movement of the holding member depending on the rotative circumferential velocity of the pressure bonding roller. The bonding apparatus may be characterized further in that the film trailing edge holding member movement speed control means includes gears for driving the pressure bonding roller, gears engaged with the former gears so as to move the film trailing edge holding member, and a coupling means for coupling the rotary shaft of the member to the latter gears so that the rotary shaft can be uncoupled therefrom. The bonding apparatus may be characterized in that the film trailing edge holding member movement speed control means includes a motor for moving the film trailing edge holding member, and a motor rotation speed control means for automatically changing the rotation speed of the motor depending on the rotative circumferential velocity of the pressure bonding roller. Since the speed control means for automatically changing the speed of the movement of the film trailing edge holding member depends on the rotative circumferential velocity of the pressure bonding roller and is provided in the bonding apparatus mentioned above, the speed of the movement of the holding member can be automatically changed depending on the rotative circumferential velocity of the roller, to reduce the likelihood that an air bubble is made between the film and the base plate or that the film is wrinkled.
The above-mentioned problems also are solved by providing a bonding apparatus in which a pressure bonding roller is provided so that a film having a length corresponding to that of a base plate is bonded to the film bonding surface of the base plate by the roller; a film trailing edge holding member is rotatably supported near the peripheral surface of the roller; and the member holding the trailing edge portion of the film cut off to the desired length is moved to a position near the mutual contact surfaces of the roller and the film on the base plate, at a speed equal to or slightly less than the rotative circumferential velocity of the roller. The bonding apparatus is characterized in that the film trailing edge holding member has a plurality of internal chambers communicating with mutually-independent suction units, respectively. The bonding apparatus may be characterized further in that the effective length of the film trailing edge holding member is not less than the maximum width of films to be bonded by the apparatus; and the longitudinal edge portion of the holding member, which is located nearer the position of the bonding of the film than the other longitudinal edge portion of the member, is shaped as a wedge.
The above-mentioned problems are solved by providing a bonding apparatus in which a pressure bonding roller is provided so that a film having a length corresponding to that of a base plate is bonded to the film bonding surface of the base plate by the roller; a film trailing edge holding member is rotatably supported near the peripheral surface of the roller; and the member holding the trailing edge portion of the film cut off to the desired length is moved to a position near the mutual contact surfaces of the roller and the film on the base plate, at a speed equal to or slightly less than the rotative circumferential velocity of the roller. The bonding apparatus is characterized in that the film trailing edge holding member has an internal chamber which is provided with suction holes communicating with a suction unit and is divided into a plurality of small internal chambers which enable the holding member to cope with various widths of films. The bonding apparatus may be characterized further in that the effective length of the film trailing edge holding member is not less than the maximum width of films to be bonded by the apparatus; and the longitudinal edge portion of the bonding member, which is located nearer the position of the bonding of the film than the other longitudinal edge portion of the member, is shaped as a wedge.
Since the film trailing edge holding member of the bonding apparatus mentioned above has the plural internal chambers communicating with the mutually-independent suction units, respectively, or has the internal chamber which is provided with the suction holes communicating with the suction unit and is divided into the plural small internal chambers which enable the holding member to cope with various widths of films, selected ones of the internal chambers can be put into sucking action depending on the width of the film to be bonded to the base plate. For that reason, the trailing edge portion of the film can be held by the holding member, regardless of the width of the film, to reduce the likelihood that an air bubble is made between the film and the base plate or that the film is wrinkled. Since the effective length of the film trailing edge holding member is not less than the maximum width of films to be bonded by the apparatus and the longitudinal edge portion of the member, which is located nearer the position of the bonding of the film than the other longitudinal edge portion of the member, is shaped as a wedge, the member can hold the trailing edge of the film until the trailing edge reaches a position nearer the pressure bonding roller, to reduce the likelihood that an air bubble is made between the film and the base plate that the film is wrinkled.